diff --git a/src/calibre/gui2/metadata/pdf_covers.py b/src/calibre/gui2/metadata/pdf_covers.py
index b53d12d70b..e04a618103 100644
--- a/src/calibre/gui2/metadata/pdf_covers.py
+++ b/src/calibre/gui2/metadata/pdf_covers.py
@@ -22,6 +22,7 @@ from calibre.gui2 import error_dialog, file_icon_provider
 from calibre.ptempfile import PersistentTemporaryDirectory
 
 class PDFCovers(QDialog):
+    'Choose a cover from the first few pages of a PDF'
 
     rendering_done = pyqtSignal()